For a few hours after a particularly loud concert, the ringing in your ears makes it tough to hear. When your friends ask how the show was, you sheepishly ask them speak up so you can catch what they’re saying. This hearing loss, which is most often reversible, doesn’t mean you’re more likely to need a hearing aid later in life. In fact, researchers found the opposite—reversible hearing loss actually protects your ears.
Researchers led by Gary Housley, chair of physiology at the University of New South Wales in Australia, exposed mice to loud noises to learn more about how reversible hearing loss works. Some of the mice had regular ears, but others had ears that lacked a receptor that accepts ATP, a chemical that the cochlea—the spiral shaped auditory part of the inner ear—releases.
The mice without the receptor could listen to loud noises for hours on end without experiencing any short-term effects. It was almost as if they could not perceive a change in sound levels. The mice with the regular ears, however, experienced short-term hearing loss that could last for more than 24 hours, but in the long run protected their ears. And even though the mice without the receptor didn’t seem to notice booming noises, they showed more evidence of permanent hearing loss.
"It's like sun exposure," says Housley. "It's not the acute exposure, but the chronic exposure, that can cause problems years later."
This paper, published in the Proceedings of the National Academy of Sciences (PNAS), reinforces what Housley discovered in a previous study about deafness. In that study he looked at two Chinese families with a mutation in their ATP receptors; if family members worked around loud noises, they experienced accelerated hearing loss.
"Because our hearing sensitivity adapts, we can withstand loud noise, but we can't sense the absolute intensity of the sound and if we exceed the safe sound upper limit, we will damage our hearing—despite this protective adaptation mechanism we have discovered,” Housley says.